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Multicomponent Remote Sensing of Vehicle Exhaust by Dispersive Absorption Spectroscopy. 2. Direct On-Road Ammonia Measurements

Baum, Marc M. and Kiyomiya, Eileen S. and Kumar, Sasi and Lappas, Anastasios M. and Kapinus, Vadym A. and Lord, Harry C., III (2001) Multicomponent Remote Sensing of Vehicle Exhaust by Dispersive Absorption Spectroscopy. 2. Direct On-Road Ammonia Measurements. Environmental Science and Technology, 35 (18). pp. 3735-3741. ISSN 0013-936X. doi:10.1021/es002046y.

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Remote sensing was employed for the first time to measure NH_3 levels in the exhaust of on-road light duty motor vehicles. The sensor also measured the concentration of CO_2, CO, hydrocarbons, and NO, among other pollutants, in the emitted exhaust. Field measurements were conducted at a Los Angeles freeway on-ramp; vehicles traveled at cruise speeds between 20 and 25 m s^(-1) (45−55 mi h^(-1)). Mean fleet NH_3 levels of 44.7 ± 4.1 ppm were observed. These emissions exhibited a highly skewed distribution:  50.1% of the emitted NH_3 was contributed by 10% of the sampled fleet. The pollutant distribution among high NH_3 emitters is analyzed to identify the conditions that lead to three-way catalyst malfunction and, hence, NH_3 formation. In contradiction with previous reports, we found that high NH_3 emissions could not be attributed to vehicles running under rich air-fuel conditions. We estimate a mean fleet NH_3 mass emission rate of 667 ± 57 mg L^(-1) (E_r = 94 ± 8 mg km^(-1)). These findings could have significant implications on air quality in the South Coast Air Basin (SoCAB) of California, since they support the hypothesis that emissions from motor vehicles constitute a dominant regional source of NH_3, between 20 and 27% of total daily emissions. As NH_3 is the predominant atmospheric base, tropospheric levels play a key role in the buffering capacity of the atmosphere and, hence, the formation of fine aerosol. Our results could explain the ubiquitous distribution of ammonium fine particles observed during fall stagnation conditions in the SoCAB.

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Additional Information:© 2001 American Chemical Society. Received 29 December 2000. Date accepted 25 June 2001. Published online 9 August 2001. Published in print 1 September 2001. This research was carried out under the sponsorship of the Mobile Source Air Pollution Reduction Review Committee (MSRC) (contract no. AB2766/96028). We gratefully acknowledge the valuable assistance provided by this program. We would like to acknowledge the support of CalTrans for issuing a permit in haste. We also thank Prof. M. R. Hoffmann of Caltech for valuable discussions. The statements and conclusions in this paper are those of the authors and not necessarily those of the MSRC or the South Coast Air Quality Management District (SCAQMD). The mention of commercial products, their sources or their uses in connection with material reported herein is not to be construed as either an actual or implied endorsement of such products.
Funding AgencyGrant Number
Mobile Source Air Pollution Reduction Review CommitteeAB2766/96028
Issue or Number:18
Record Number:CaltechAUTHORS:20170316-102145589
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Official Citation:Multicomponent Remote Sensing of Vehicle Exhaust by Dispersive Absorption Spectroscopy. 2. Direct On-Road Ammonia Measurements Marc M. Baum, Eileen S. Kiyomiya, Sasi Kumar, Anastasios M. Lappas, Vadym A. Kapinus, and Harry C. Lord III Environmental Science & Technology 2001 35 (18), 3735-3741 DOI: 10.1021/es002046y
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75179
Deposited By: Ruth Sustaita
Deposited On:16 Mar 2017 22:48
Last Modified:15 Nov 2021 16:31

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